Method of forming fluorine doped boron-phosphorous silicate glass (F-BPSG) insulating materials

ABSTRACT

In one aspect, the invention includes a method of forming an insulating material comprising: a) providing a substrate within a reaction chamber; b) providing reactants comprising a Si, F and ozone within the reaction chamber; and c) depositing an insulating material comprising fluorine, silicon and oxygen onto the substrate from the reactants. In another aspect, the invention includes a method of forming a boron-doped silicon oxide having Si—F bonds, comprising: a) providing a substrate within a reaction chamber; b) providing reactants comprising Triethoxy fluorosilane, a boron-containing precursor, and ozone within the reaction chamber; and c) depositing a boron-doped silicon oxide having Si—F bonds onto the substrate from the reactants. In yet another aspect, the invention includes a method of forming a phosphorus-doped silicon oxide having Si—F bonds, comprising: a) providing a substrate within a reaction chamber; b) providing reactants comprising triethoxy fluorosilane, a phosphorus-containing precursor, and ozone within the reaction chamber; and c) depositing a phosphorus-doped silicon oxide having Si—F bonds onto the substrate from the reactants.

TECHNICAL FIELD

The invention pertains to methods of forming insulating materials, suchas, for example, materials comprising silicon oxide. In exemplaryapplications, the invention pertains to methods of forming boron and/orphosphorous doped materials comprising fluorine, silicon and oxygen.

BACKGROUND OF THE INVENTION

Silicon oxide materials (such as, for example, silicon dioxide) arecommonly used in semiconductor device fabrication as insulatingmaterials. Silicon oxide materials can be formed by chemical vapordeposition (CVD) from appropriate precursors. An exemplary combinationof precursors that can be utilized for forming silicon oxide materialsis silane (SiH₄) and hydrogen peroxide (H₂O₂). Another precursorcombination which can be utilized for forming silicon oxides istetraethyl orthosilicate (TEOS) and ozone (O₃).

Silicon oxide materials can be doped with one or both of boron andphosphorous to alter (lower) a dielectric constant of the material. Theboron and/or phosphorous can be introduced into a silicon oxide materialby, for example providing one or both of a boron-containing precursormaterial and a phosphorous precursor material in a CVD reaction chamberduring deposition of the silicon oxide material. Suitable phosphorousprecursor materials include, for example, PH₃ and tetraethoxy phosphine(TEPO). Suitable boron-containing precursors include, for example, B₂H₆and triethyl borane (TEB). An alternative method of introducingphosphorus and/or boron into a silicon oxide material is to implant oneor both of phosphorus and boron into the material.

A characteristic of a deposited silicon oxide material is its so-calledflow temperature. A flow temperature is a temperature at which thesilicon oxide material will melt. Flow temperature can be an importantcharacteristic of silicon oxide materials. For instance, incorporationof silicon oxide materials into semiconductor fabrication processesfrequently involves melting and reflowing of the materials to increaseplanarity and obtain good coverage of the materials over underlyingdevice structures. Films consisting essentially of silicon dioxidetypically have flow temperatures of about 1,100° C. or higher. Additionof boron or phosphorous to such films can reduce the flow temperaturesto less than 850° C. It would be desirable to further reduce flowtemperatures. Specifically, silicon oxide flow frequently occurs afterprovision of semiconductor devices in a semiconductor fabricationprocess. The high temperatures of silicon dioxide reflow can adverselyaffect such devices.

Another characteristic of silicon oxide materials is density. Densermaterials generally have better flow properties than less densematerials. Specifically, denser materials can frequently reflow overunderlying nonplanar structures more quickly than can less dense siliconoxide materials. Accordingly, it would be desirable to develop methodsfor densifying silicon oxide materials.

SUMMARY OF THE INVENTION

In one aspect, the invention encompasses a method of forming aninsulating material. A substrate is provided within a reaction chambertogether with reactants comprising Si, F and ozone. An insulatingmaterial comprising fluorine, silicon and oxygen is deposited onto thesubstrate from the reactants.

In another aspect, the invention encompasses a method of forming aboron-doped silicon oxide having Si—F bonds. A substrate is providedwithin a reaction chamber together with reactants comprising F-TES, aboron-containing precursor, and ozone. A boron-doped silicon oxidehaving Si—F bonds is deposited onto the substrate from the reactants.

In yet another aspect, the invention encompasses a method of forming aphosphorus-doped silicon oxide having Si—F bonds. A substrate isprovided within a reaction chamber together with reactants comprisingF-TES, a phosphorus-containing precursor, and ozone. A phosphorus-dopedsilicon oxide having Si—F bonds is deposited onto the substrate from thereactants.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

The invention encompasses methods of chemical vapor deposition ofinsulating materials comprising fluorine, silicon and oxygen. In oneaspect, the invention encompasses a method wherein a substrate isprovided within a CVD reaction chamber together with reactantscomprising Si, F and ozone. Subsequently, an insulating materialcomprising fluorine, silicon and oxygen is deposited onto the substratefrom the reactants.

In an exemplary embodiment of the invention, the Si and F are comprisedby a compound having an Si—F bond, such as, for example F-TES (triethoxyfluorosilane). The F-TES is preferably flowed into the reaction chamberat a rate from about 100 milligrams per minute (mg/min) to about 500mg/min. The ozone is preferably flowed into the reaction chamber as amixture with O₂ (the mixture preferably containing from about 5% toabout 15% ozone, by volume), with an example being at a rate from about1000 standard cubic centimeters per minute (sccm) to about 5000 sccm,and preferably about 2000 sccm. In addition to the F-TES and ozone, asecond silicon precursor can be flowed into the reaction chamber. Suchsecond silicon precursor can comprise, for example, TEOS. In alternativeembodiments of the invention, the Si reactants can comprise TEOS and theF reactants can be comprised by molecules lacking Si.

Temperature of the substrate within the reaction chamber is preferablymaintained at from about 400° C. to about 700° C., and more preferablymaintained at about 500° C. Pressure within the reaction chamber ispreferably maintained at from about 1 Torr to about 1 atmosphere, morepreferably at from about 400 Torr to about 1 atmosphere, and even morepreferably at about 600 Torr. Most preferably, no plasma is presentwithin the CVD reaction chamber to reduce costs and process complexity.However, it is noted that the invention encompasses embodiments whereinplasma is present within the reaction chamber during the depositionprocess.

Under the above-described exemplary conditions, a material comprisingfluorine, silicon and oxygen is deposited onto the substrate at a ratefrom about 500 Å/minute to about 10,000 Å/minute, and is typicallydeposited at a rate of about 8,000 Å/minute. The deposited materialcomprises silicon oxide interspersed with Si—F bonds. The fluorine isgenerally present in such material to a concentration from about 0.1atomic percent to about 10 atomic percent.

An advantage of incorporating fluorine into a silicon oxide material isthat the fluorine can reduce the flow temperature of the material. Forinstance, it is found that fluorine incorporation into a silicon oxidematerial to an amount of from about 0.1 atomic percent to about 10atomic percent can reduce a flow temperature of the material.Specifically, it is found that a flow temperature of the material can bereduced by from about 50° C. to about 100° C. relative to a siliconoxide material that is identical to the fluorine-containing material inall respects except for lacking the fluorine.

Another advantage of incorporating Si—F bonds into a silicon oxidematerial (such as, for example, SiO₂ or borophosphosilicate glass) isthat the fluorine can decrease a dielectric constant of the material.

Yet another advantage of incorporating fluorine into a silicon oxidematerial can be to reduce so-called fixed charge problems. Fixed chargesresult when one or more silicon atoms are bonded to less than four otheratoms. In such circumstances, the silicon atoms can carrypositively-charged electron density and shift a threshold voltage of adevice incorporating the silicon atoms. Negatively charged fluorineatoms can interact with the positively-charged electron density toneutralize the density and alleviate fixed charge problems that wouldotherwise occur.

It is noted that F-TES has been utilized in the prior art in CVDprocesses for depositing silicon oxide materials. However, the F-TES wasnot utilized in combination with ozone. An aspect of the presentinvention is recognition that chemical vapor deposition offluorine-containing silicon oxide from reactants comprising F-TES can besignificantly improved if such reactants further comprise ozone.Specifically, it is recognized that if the reactants comprise F-TES andlack ozone, very little fluorine is incorporated into a depositedsilicon oxide. The advantageous effects of ozone have not been seen withother oxygen-containing precursors. Specifically, it is found that O₂and/or H₂O₂ work significantly less well than ozone as co-reactants withF-TES. In other words, if a comparable concentration of H₂O₂ or O₂ isutilized under the above-described reaction conditions in substitutionof ozone, the silicon oxide that is formed will have significantly lessthan 0.1 atomic percent fluorine incorporated therein. Such silicondioxide will have higher flow temperatures and less density than apreferred silicon oxide formed according to a method of the presentinvention utilizing ozone in a chemical vapor deposition process. Also,H₂O₂ can be more difficult to work with than ozone. For instance, it canbe more difficult to accurately control an H₂O₂ concentration in areaction chamber than to control an ozone concentration in the chamber.

In other aspects of the invention, a fluorine-containing silicon oxidecan be provided to be doped with, for example, one or both ofphosphorous and boron. For instance, a phosphorous precursor can beincorporated as a reactant in a chemical vapor deposition process of thepresent invention to form an insulating material comprising fluorine,silicon, oxygen, and phosphorous. The phosphorous precursor cancomprise, for example, TEPO. Preferably, the amount of phosphorousincorporated into a fluorine-containing silicon oxide of the presentinvention is from about 1 atomic percent to about 10 atomic percent.

Exemplary conditions for incorporating phosphorous into afluorine-containing silicon oxide utilizing a CVD process include:

a pressure within a CVD reaction chamber of from about 1 Torr to about 1atmosphere;

a temperature of a substrate within the chamber of from about 400° C. toabout 700° C.;

a flow rate of F-TES into the reaction chamber of from about 100 mg/minto about 500 mg/min;

a flow rate of ozone-containing gas (provided as a mixture of from about5% to about 15% ozone in O₂) of from about 1000 sccm to about 5000 sccm;and

a flow rate of TEPO in the reaction chamber of from about 25 mg/min toabout 400 mg/min.

As another example, boron can be incorporated into a fluorine-containingsilicon oxide of the present invention by providing a boron-containingprecursor as a reactant in a CVD reaction chamber. The boron-containingprecursor can comprise, for example, TEB. The boron is preferablyprovided in a fluorine-containing silicon oxide of the present inventionto a concentration of from about 1 atomic percent to about 10 atomicpercent, and more preferably provided to a concentration of less than orequal to about 8 atomic percent.

An exemplary process for incorporating boron into a fluorine-containingsilicon oxide utilizing a CVD process includes:

a pressure within a CVD reaction chamber of from about 1 Torr to about 1atmosphere;

a temperature of a substrate within the chamber of from about 400° C. toabout 700° C.;

a flow rate of F-TES into the reaction chamber of from about 100 mg/minto about 500 mg/min;

a flow rate of ozone-containing gas (provided as a mixture of from about5% to about 15% ozone in O₂) of from about 1000 sccm to about 5000 sccm;and

a flow rate of TEB into the reaction chamber of from about 25 mg/min toabout 400 mg/min.

In yet another exemplary application, a fluorine-containing siliconoxide of the present invention can be provided to be doped with bothboron and phosphorous. Preferably, the boron and phosphorous atoms aretogether provided to a concentration of from about 3 atomic percent toabout 12 atomic percent within the fluorine-containing silicon oxide. Anexemplary composition of the silicon oxide comprises about 3% boron,about 7% phosphorous, and about 2% fluorine (by atomic percent).

Exemplary conditions for forming the boron and phosphorous dopedfluorine-containing silicon oxide include:

a pressure within a CVD reaction chamber of from about 1 Torr to about 1atmosphere;

a temperature of a substrate within the chamber of from about 400° C. toabout 700° C.;

a flow rate of F-TES into the reaction chamber of from about 100 mg/minto about 1000 mg/min;

a flow rate of ozone-containing gas (provided as a mixture of from about5% to about 15% ozone in O₂) of from about 1000 sccm to about 8000 sccm;

a flow rate of TEPO in the reaction chamber of from about 25 mg/min toabout 400 mg/min; and

a flow rate of TEB into the reaction chamber of from about 25 mg/min toabout 400 mg/min. In preferred embodiments, the pressure is from about10 Torr to about 700 Torr.

In each of the above-described embodiments, the CVD reaction chamberreferred to is a single wafer, cold wall chamber. The inventionencompasses embodiment utilizing other types of reaction chambers.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

What is claimed is:
 1. A method of forming a boron and phosphorus dopedsilicon oxide having Si—F bonds, comprising: providing a substratewithin a CVD reaction chamber at a pressure of from about 1 Torr toabout 760 Torr and at a substrate temperature of from about 400° C. toabout 700° C.; flowing F-TES into the reaction chamber at a flow rate offrom about 100 mg/min to about 1,000 mg/min; flowing an ozone-containinggas into the reaction chamber at a flow rate of from about 1,000 sccm toabout 8,000 sccm, the gas containing a mixture of from about 5 vol % toabout 15 vol % ozone in O₂; flowing TEPO into the reaction chamber at aflow rate of from about 25 mg/min to about 400 mg/min; flowing TEB intothe reaction chamber at a flow rate of from about 25 mg/min to about 400mg/min; providing the F-TES, ozone-containing gas, TEPO, and TEBsimultaneously in the reaction chamber; and depositing a boron andphosphorous doped silicon oxide having Si—F bonds onto the substrate ata rate of from about 500 Å/min to about 10,000 Å/min with a plasmapresent in the reaction chamber, the doped silicon oxide comprising fromabout 3 atomic % to about 12 atomic % total of boron and phosphorous,comprising from about 0.1 atomic % to about 10 atomic % flourine,comprising more flourine than occurs in a doped silicon oxide depositedfrom an otherwise identical method using O₂ or H₂O₂ instead of O₃,exhibiting a flow temperature that is from about 50° C. to about 100° C.less than occurs in an otherwise identical doped silicon oxide lackingthe fluorine, exhibiting a dielectric constant that is less than occursin an otherwise identical doped silicon oxide lacking the fluorine, andexhibiting a fixed charge that is less than occurs in a doped siliconoxide deposited from an otherwise identical method using TEOS instead ofF-TES.
 2. The method of claim 1 wherein the CVD reaction chambercomprises a single wafer, cold wall chamber.
 3. The method of claim 1wherein the pressure comprises from about 10 Torr to about 700 Torr. 4.The method of claim 1 wherein the pressure comprises from about 400 Torrto about 700 Torr.
 5. The method of claim 1 wherein the doped siliconoxide comprises from about 2 atomic % to about 10 atomic % flourine. 6.The method of claim 1 wherein the doped silicon oxide comprises 2 atomic% fluorine.
 7. The method of claim 1 wherein the depositing occurs at arate of from about 8,000 Å/min to about 10,000 Å/min.
 8. The method ofclaim 1 wherein the pressure is 600 Torr, the substrate temperature is500° C., the ozone-containing gas flow is 2,000 sccm, the depositionrate is 8,000 Å/min, the boron composition is 3 atomic %, and thephosphorous composition is 7 atomic %.